11,11,12,12-tetracyano-naphtho-2,6-quinodimethan and its anion-radical salts



United States Patent 3,226,389 11,11,12,12-TETRACYANO-NAPHTHO-2,6-QUHNO- DIMETHAN AND ITS ANION-RADICAL SALTS Walter H. Hertler, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a

corporation of Delaware N0 Drawing. Filed Jan. 4, 1%2, Ser. No. 164,379 Claims. (Cl. 260--283) This invention relates to 11,11,12,12-tetracyanonaphtho- 2,6-quinodimethan (referred to hereinafter as suitable for brevity as TNAP), and is more particularly concerned with charge-transfer salts of the anion-radical of TNAP with Lewis bases broadly, and with a process for preparing TNAP and the charge-transfer salts of the anion-radical of TNAP.

Most of the possible position isomers of the parent naphthoquinodimethan hydrocarbon structure have at least been formulated in the literature and some, for instance, the l,4-isomer, probably have been obtained. The 2,6- isoiner was referred to by Szwarc, J. Poly. Sci, 6, 319 1951), but only with respect to unsuccessful attempts to obtain the polymer from 2,6-dimethylnaphthalene. 11,11, 12,1Z-tetraphenylnaphtho-2,6-quinodimethan has been referred to by several authors, e.g., Pullman et 211., Les Theories Electroniques de la Chirnie Organique, Masson editor, Paris, 1952. However, no naphthoquinodimethan derivative has been reported wherein any functional substituent is present, either on ring carbon or on the exocyclic methylene carbon, particularly of the 2,6-isomer where the quinoid conjugation involves two double bonds in each of the two rings.

It is an object of this invention to provide naphthoquinodimethan derivatives having functional substituents. It is a further object of this invention to provide charge-transfer salts of the 11,11,12,1Z-tetracyanonaphtho-2,6-quinodimethan anion-radical with Lewis bases broadly. A still further object of this invention is to provide a process for preparing 11,11,12,IZ-tetracyanonaphtho 2,6 quinodimethan itself and the aforesaid charge-transfer salts of the anion-radical thereof. Other objects of this invention will appear hereinafter.

These and, other objects of this invention are accomplished by means of a process which proceeds according to the following stoichiometry based on 2,6-dimethylnaphthalene.

CH3 2NBS CH2B1 H30- BrHz lNaON CIN NO $11 (Etohco -CH2CN 1 COOEt HC NCH2C lNHa NC 011 P 0 on I AJONHQ HC 2 HC 1 IIENOC 3,226,389 Patented Dec. 28, 1965 "ice In the foregoing synthesis, the cation is that of a Lewis base; and, in the symbol indicates a negative ionic charge and indicates an electron. As will be seen from this stoichiometry, the 2,6- diniethylnaphthalene is dihalogenated wih, for instance, N-bromosuccinimide (NBS) and converted to the dinitrile by metathesis with an alkali metal cyanide. The 'dinitrile is carboalkoxylated to form the bis-cyanoacetic ester derivative which in turn is converted to the cyanoacetamide derivative which in turn is dehydrated with a strong dehydrating agent to form the tetranitrile which in turn is oxidized, or more properly, dehydrogenated, to 11,11,12, lZ-tetracyanonaphtho-2,6-quinodimethan, which in turn when treated with a source of the desired Lewis base forms a charge-transfer salt of the TNAP anion-radical, i.e., the l 1,1 1,12,lZ-tetracyanonaphtho-Z,6-quinodimethanide.

The first step does not necessarily have to involve preparation of the dibromide since the dichloride and diiodide can also be used. However, for reasons for convenience combined with easy preparability and good reaction efliciency, the dibromide is preferred. Convenient sources of the necessary bromine, chlorine, or iodine atoms are the corresponding N-bromo-, N-chloro-, and N-iodosuccinimides. Alternatively, and preferably in the case of the iodides, the bromides or chlorides can be prepared and converted to the desired other halide by suitable metathesis.

The metathetical conversion to the dinitrile does not have to involve sodium cyanide since any other alkali metal cyanide, such as lithium and potassium, can likewise serve. Also quaternary cyanides such as tetraethylammonium cyanide can be used. However, again for reasons of convenience and over-all reaction efliciency, as well as cost, sodium cyanide is much preferred.

The carboalkoxylation reaction can be carried out with any convenient source of this group, including the alkyl carbonates. However, again for reasons of convenience, balanced reactivity, and cost, diethyl carbonate is preferred.

The conversion of the cyanoacetic ester to the biscyanoacetamide intermediate can be done with any convenient source of the necessary ammonia. For reasons of cost and availability, ammonia itself is preferred.

The dehydration stage from the biscyanoacetamide derivative to the tetranitrile can be efiected by any suitable chemical dehydrating agent, such as phosphorus pentoxide, benzenesulfonyl chloride/ pyridine, and the like, or, if desired, the dehydration step can be accomplished thermally, simply by heating the compound to 400 C. or thereabouts.

The oxidation, or more properly dehydrogenation, step can be effected with any suitable oxidant, such as selenium dioxide directly, or the oxidation can be achieved indirectly by a combined halogenation/dehydrohalogenation reaction, such as the use of N-chloro-, N-bromo-, or N-iodosuccinimide, alone or with other halogenation means. Alternatively, the halogenation can be effected directly with the necessary halogen, e.g., chlorine, bromine, or iodine. Once halogenation has been achieved, dehydrohalogenation appears to occur spontaneously except possibly with the iodine where an added dehydrohalogenation agent such as pyridine may be needed.

As shown in the foregoing series of equations, the above reactions convert the initial reactant, 2,6-dimethylnaphthalene, to ll,11,12,12-tetracyanonaphtho2,6-quinodimethan, or TNAP. The salt charge-transfer compounds between Lewis bases and TNAP are then obtained by reacting TNAP directly or indirectly with the requisite Lewis base.

This invention is generic to TNAP and the chargetransfer compounds of TNAP with Lewis base. These can broadly be formulated as wherein n is the formal positive charge on the cation M; x is the number of said cation species present, which in the plural instance includes mixed individual cations; nx is the total negative charge on the charged TNAP moieties, i.e., the charge-transfer compound is overall electronically neutral; y is the number of negatively charged TNAP species present; and z is the number of combined neutral species present, if any, where the combined neutral species are indicated by the indicates a negative ionic charge and an electron, and x, y, and z are numbers, alike or different, both whole and fractional, x and y being from 1 to 6, and z from to 6. Thus, broadly speaking, these charge-transfer compounds can be described in two general types of the formulas i.e., the simple salts wherein there are no combined neutral species, and

i.e., the complex salts where z is a number from 1 to 6. A specific example is the amine charge-transfer complex salt N-n-propylquinoliniurn (TN AP) T TNAP) The charge-transfer compounds include those with the simple monovalent anion-radicals (TNAP) in which one electron has been transferred per TNAP species. These can be illustrated by the structures x[ NAPFLX, (M ,.[(TNAP (TNAP) )x Y J XK AP 1 (TNAP) O 1 Y and the like.

The invention also obviously includes the charge-transfer compounds where more than one electron has been transferred in one or more TNAP moiety, e.g., of the and the like.

These all represent electronic resonance hybrid structures. In the latter group different electronic configurations in the sence of the number of electrons involved per moiety differ but the overall charge of the complexes in all cases remain neutral. As is conventionally accepted, it is not intended to represent structurally all the resonance hybrids contributing to the stable ground state of any one of these charge-transfer compounds. For convenience and brevity throughout this specification, the single anion-radical representation will be used, i.e., in the format (TNAP) to include thereby all possibly contributing electronic resonance hybrid forms.

It is also intended to include in these charge-transfer compounds, including compounds containing more than one cation per molecule, defect-type structures quite parallel to the well-known oxygen-deficient metal oxides, as well as the metal-deficient metal oxides. Thus, these charge-transfer compounds include species which can be sufiicient in either or both the cation or anion portions.

The present invention is generic not only to 11,11,12, 12-tetracyanonaphtho-2,6-quino-dimethan but also the charge-transfer compounds thereof with Lewis bases broadly, including specifically organic and organo-inorganic Lewis bases. Charge-transfer compounds of previously known Lewis acids with Lewis bases are well known in the art. Frequently these charge-transfer compounds were referred to as Pi complexes. More recently, the concept has become well established that such complexes are more properly described as charge-transfer compounds-see, for instance, Mulliken, J. Am. Chem. Soc. 74, 811 (1952). The charge-transfer compounds of TNAP with Lewis bases range in degree of charge transfer from those of true complex structure to those where actual and complete charge transfer exists in the ground electronic state. Compounds of the last-mentioned type constitute so-called anion-radical salts wherein at least one molecule of TNAP carries a transferred electron, and accordingly a negative electronic charge, and at least one molecule of the Lewis base component has donated at least one electron to the TNAP component and accordingly has an electron deficiency from its original form, and, therefore is more positive. The invention is generic to those charge-transfer compounds of TNAP with Lewis bases which exhibit a detectable paramagnetic resonance absorption under normal conditions. It is likewise generic to TNAP charge-transfer compounds wherein the maximum charge transfer occurs not in the ground electronic state but rather in the excited state (see Orgel, Quart. Rev. Chem. 8, 1422 (1954) for a discussion of this type of normally diamagnetic charge-transfer compounds) Lewis bases which, with TNAP, form the necessary second component for forming the charge-transfer compounds of TNAP are well known to the chemical art (see G. N. Lewis, J. Franklin Inst. 226, 293 (1938) and following papers by Lewis and several co-authors). Broadly speaking, the Lewis base is, by definition, a molecule, the structure or configuration of which, electronically speaking, is so arranged that the molecule is capable of donating one or more electrons to a molecule which has an electron-deficient structure. Many and varied electron donor compounds are known. To list but a few well-recognized such classes there need only be named: the amines and various alkyl and aryl hydrocarbon-substituted amines which may be described structurally by the following two formulas:

where R R R are H, alkyl, or alkylene up to 10 carbons and when R is aryl, R and R are H or alkyl up ,5. to 20 carbons, and the corresponding quaternary ammonium salts as below,

where the amino substituents are ortho or para to each other and R R R R are alkyl up to 20 carbons and Q, X, Y, Z are H or hydrocarbon up to 20 carbons, which can be together joined, or other orthoor paradirecting substituents with the provisos that (1) when R R R and R are alkyl, Q and X are H, (2)

when R and R are aryl, R and R are H or alkyl, and

(3) where Q-X and/ or YZ taken pairwise are cycloalkylene or fused aromatic, R and R are H, and the corresponding quaternary ammonium salts wherein the quaternary radical is another R R R R and any of the usual anions is involved.

Also included are the substituted amines of the alkyl and aryl hypdrocarbon-substituted types defined by the foregoing two structural formulas wherein R R R and/or R are variously oxaalkylene or thiaalkylene or oxaalkyl or thiaalkyl, e.g., 4-thiapiperidine, as well as the hydroiodides of the foregoing primary, secondary, or tertiary amines, and also the corresponding quaternary ammonium iodides, e.g., morpholine hydroiodide; all heterocycles containing nuclear nitrogen and the hydroiodides or alkyl iodide salts thereof; substituted ethylenes of the type R Rn wherein from one to four of the R R R or R groups are amino or alkylamino, any remaining being alkyl, alkoxy, alkoxythio, aryl, aryloxy, or arylthio; and the hydroiodide or alkyl iodide salts thereof, including the plain iodides, e.g., of the aminium type RZNTF and the Wurster iodides of aromatic amines, e. g., Wursters blue iodide,

(in the foregoing diamines, it is expressly intended to include polynuclear diarnines in which the nitrogens are connected by a conjugated system), the phosphines and alkyl or aryl hydrocarbon-substituted phosphines:

l a Rr-P where R R and R are alkyl or aryl up to 20 carbons (the aryls being unsubstituted or having and p-directing substituents),

where R R Q, X, Y, and Z are as above in the aryl amine analogs except that R and R cannot be H, and the corresponding quaternary phosphonium salts wherein the quaternary radical is another R R R and any of the usual anions is involved;

6 the arsines and alkyl and aryl hydrocarbon-substituted arsines:

R2 R1AS in wliere R R and R are as above in the phosphine ana- As-R Z 1 1 where R R Q, X, Y, and Z are as above in the aryl phosphine analogs, and the corresponding quaternary arsonium salts wherein the quaternary radical is another R R R and any of the usual anions is involved;

the stibines and alkyl and aryl hydrocarbon-substituted stibines:

Rr-Sb 1'1,

where R R and R are as above in the arsine analogs,

Where R R Q, X, Y, and Z are as above in the aryl arsine analogs, and the corresponding quaternary stibonium salts wherein the quaternary radical is another R R R and any of the usual anions is involved;

the quaternary ammonium bases or their salts, such as In all the foregoing instances, the molecular structure in the hydrocarbon moieties can also carry functional substituents. The preferred substituents can be classed as those which, when present on ring carbon of an aromatic nucleus, tend to direct any entering substituent radical into the orthoor para-position, i.e., the so-called orthopara orienting groups. These substituents have also been described by Price, Chem. Rev. 29, 58 (ll94l), in terms of the electrostatic polarizing force as measured in dynes of the said substituent groups on an adjacent double bond of the benzene nucleus. Quantitatively, any substituent which has or exhibits an electrostatic polarizing force in dynes less than 0.50 can be regarded as ortho-para orienting and electropositive, and is preferred here. These preferred substituents include: alkyl hydrocarbon up to 20 carbons; substituted alkyl up to 20 carbons, e.g., aminoalkyl, hydroxyalkyl, alkoxyalkyl, vinylalkyl, haloalkyl; hydroxy; alkoxy up to 20 carbons; thiol, alkyl thiol (up to 20 carbons); amino; N-alkylamino or N,N-dialkylamino with alkyls up to 20 carbons; N-monoarylamino; and the like.

Suitable specific Lewis bases for making the TNAP/ Lewis base chargetransfer compounds in molar ratios from 2/1 to 1/2 are given in the following list. In connection with the molar ratios just given, it is to be understood that the present charge-transfer compounds lie within the arithmetical range of the two molar ratio extremes and not solely at the extremes. Thus, charge-transfer compounds of the present invention are inclusive of, for instance, 3/2, 1.5/1, and the like TNAP/Lewis base charge-transfer compounds. Useful specific Lewis bases include: ammonia, and amines, such as ethylamine, methylamine, dibutylamine, tridecylamine, and the like; diamines, such as 2,3-N,N,N,N'-hexamethyl-p-phenylenediamine, N,N'-dioctyl-1,5-diaminonaphthalene, 1,4-diamino- 5,6,7,S-tetrahydronaphthalene, and the like; phosphines and diphosphines, such as triphenylphosphine, tributylphosphine, ethyldioctylphosphine, 1,4-bis(diethylphosphino)benzene, and the like; ammonium and quaternary ammonium bases and salts, such as ammonium iodide, ethyltrimethylammonium iodide, dioctylammonium iodide, methyl-tri-n-propylammonium iodide, tetramethylammonium hydroxide, and the like; metals, such as Na, K, Li, Ag, Cu, and the like; metal precursors, such as the carbonyls, iodides, cyanides, e.g., iron and cobalt carbonyls, iodides, cyanides, and the like, metal chelates, such as copper salicylaldimine, cobalt pyrrolealdehydeimine, nickel 4-methoxysalicylaldoxime, copper 5-methoxy-8- quinolinolate, and the like; heterocyclic aromatic amines, phenols, and ethers, such as 4-aminopyridine, 3-hydroxyacridine, 3-dimethylaminocarbazole, 2-methoxyphenazine, and the like; aromatic hydrocarbon others, such as phenetidine, N,N-diethylanisidine, and the like; aromatic hydrocarbons and alkyl substituted aromatic hydrocarbons, including polynuclear, such as chrysene, coronene, hexamethylbenzene, 2-ethylphenanthrene, and the like.

The charge-transfer compounds of the present invention, comprising the first-discussed class wherein the TNAP moiety is present wholly in anion-radical form, are best described as simple salts of the TNAP anionrapical, i.e.,

TNAP

The cations in these simple charge-transfer anion-radical salts can equally well be organic or inorganic. These simple salts can be prepared directly by simple interaction between a suitable source of the cation and the TNAP, or, preferably, by metathetical reaction between a suitable source of a cation and a conveniently soluble source of the TNAP anion-radical, e.g., lithium TNAPide which is easily preparable directly from a suitable lithium salt, e.g., lithium iodide, and TNAP, and has the advantage in further metathetical reactions of good solubility as the simple salt plus the further significant advantage that the by-product lithium salts arising from the metathesis are also usually highly soluble so that they remain in solution while much less soluble desired charge-transfer product precipitates. In the case of the simple anion-radical salts involving organic cations, the organic quaternary halides are most generally operable. Simple hydrohalide salts of the organic cations often fail to give the simple product because of formation of free TNAP resulting in the formation of the complex charge-transfer compounds of the second type, discussed above, containing combined neutral TNAP. However, in the case of the strongly basic organic cations, speaking in the sense of basicity as conferred by an unshared pair of electrons, the organic cation hydrohalide salts are fully operable in the metathesis to give the simple salts. To be specific, for in- 8 stance, the tris(lower alkyl)-ammonium hydrohalide salts are fully operable to give the simple salts.

Most of these simple anion-radical salts, including both the organic and inorganic type, are completely ionic. However, the invention is inclusive of a broader scope for these simple anion-radical salts in that it includes compounds of very weak charge-transfer bonding, more properly described as Pi complexes, as well as the previously discussed wholly anionic, electrostatically bonded charge-transfer compounds with complete charge transfer. Thus, the invention is also inclusive of the anion-radical salts of the Wiirster type involving cation radicals. Depending on the base strength, as previously defined, of the cation moiety and the cation radical, these simple salts will involve full charge transfer, i.e., be anionic, or only partial charge transfer of the Pi complex type. Thus, bis (dimethylammonium) bis (dimethylamino ethylene diiodide with two molar proportions of lithium TNAPide forms the full charge-transfer dianiondiradical salt, bis(dimethylammonium) bis dimethylamino ethylene bis (TNAPide); whereas, 1-dimethylammonium-4-dimethylaminobenzene perchlorate, i.e., N,N,N,N'-tetramethyl-pphenylenediamine monoperchlorate, in metathesis with lithium TNAPide forms the 1/1 tetramethyl-p-phenylenediamine/TNAP Pi complex.

The metathetical reactions will generally be carried out with the lithium TNAPide, or Whatever other soluble source of the TNAP anion-radical is being used, in solution in a suitable solvent, to which solution will be added a solution of a source of the cation involved in the same or other suitable solvent. The upper temperature limit is defined by the atmospheric pressure boiling point of the highest boiling solvent if and when a mixture is used. For a single solvent system, the normal boiling point of that solvent is the preferred upper limit. If one wishes to operate at higher temperatures (e.g., under pressure or with higher boiling solvents), one should keep below the melting point of the anticipated product since the likelihood of decompositional side reactions increases at higher temperatures. This is particularly true when using solvolytic solvents so that nucleophilic displacement of substituent groups is minimized. A practical safe upper limit would be 150 C.

Formation of large crystals is customarily favored by mixing reagents at an elevated temperature and cooling at a slow rate without mechanical mixing, e.g., at a minimum cooling rate of 3 C. per hour, i.e., mix at about C. and then cool to room temperature during the succeeding 24 hours. Holding at the high temperature for too long may allow side reactions to occur to an undesirable extent. Cooling much below room temperature is not especially desirable even in the organic systems, but 5 C. is a practical lower limit. Should microcrystals be desired, reactants should be dissolved singly at the lowest temperature which will give about an 0.1 molar solution, then mixed rapidly with vigorous agitation and rapid cooling. Before mixing, the individual reactant concentration should be between about 0.001 and 0.1 molar.

The second class of these charge-transfer compounds of the TNAPides, i.e., those containing, in addition to the requisite stoichiometric amount of the TNAP anionradical to achieve electrical neutrality, additional combined proportions of neutral TNAP, has the generic structural formula:

Most of this class of the anion-radical/neutral TNAP salts with such extremely interesting electrical properties are characterized by having a cation moiety which involves a planar aromatic structure, e.g., 2/1 TNAP/ quinolinium, -N-methylquinolinium, -N-propylquinoliniurn, -4-cyano-N-methylquinolinium, -pyridinium, -1-methyl-2 (p dimethylaminophenylamino)quinolinium, -2,2'- dipyridylinium, and -1-methyl-2-(p-dimethylaminophenylazo)pyridinium salts. While this quality of the cation containing a planar aromatic structure is obviously a sufficient condition for these high electrical conductivities and allied other interesting properties, it is not a necessary one since salts of the TNAP anion-radical with other cations exhibit some of these desirable electrical properties, e.g., the TNAP/triethylammonium, -tetraethylammonium, and -diazabicyclooctane complex salts, which cations are not planar.

This second broad class of the TNAP anion-radical salts, i.e., those containing the combined neutral TNAP, will be prepared under temperature and concentration conditions, and in general using the same solvent systems, as already discussed in detail for the simple anion-radical salts. This type of salt is normally obtained directly by reaction of the source of the cation, e.g., an alkali metal halide or a substituted quaternary ammonium halide, with TNAP directly. The most useful halides, by virtue of solubility and reactivity considerations, are the iodides. With these, since the by-product of the reaction is iodine, it is generally preferred to use a large excess of the quaternary ammonium iodide reactant so as to permit scavenging of the liberated iodine in the form of the substituted I3 anion.

Another general method for the formation of these TNAP anion radical salts containing portions of combined neutral TNAP involves interaction of the source of the cation, in neutral form, with both dihydroTNAP and TNAP, for instance, according to the following equation:

In the case of the inorganic TNAP anion-radical salts containing the combined neutral TNAP, these products are obtainable most conveniently by iodide discharge from the necessary cation iodide in reaction with TNAP in organic systems. The complex inorganic cation ionradical salt with combined neutral TNAP can also be prepared by the reaction of TNAP in organic systems on the preformed simple anion-radical salt. Simple metathesis of an alkali metal TNAPide in all instances results only in formation of the simple anion-radical salt involving cation exchange.

Of course, it is within the purview of the present invention to prepare first simple anion-radical salts and convert these, if desired, to the more complex salt-containing combined neutral TNAP simply by the addition of the requisite portions of the TNAP required to a solution of the simple anion-radical charge-transfer salt.

The invention is illustrated in further detail by the following examples, in which the parts given are by weight. Examples I to VI are illustrative of individual steps involved in the process of conversion of 2,6-dimethylnaphthalene to 11,11,12,12-tetracyanonaphtho-2,6-quinodimethan, or T NAP. The remaining examples demonstrate the preparation of simple and complex salt chargetransfer compounds between Lewis bases and TNAP.

EXAMPLE I A mixture of 50 parts of 2,6-dimethylnaphthalene, 120 parts of N-bromosuccinimide, 1280 parts of carbon tetrachloride, and 0.2 part of benzoyl peroxide was stirred at the reflux under nitrogen for four hours, then 0.5 part of azobis(isobutyronitrile) was added and the mixture was heated at the reflux, with stirring, for an additional 24 hours. The reaction mixture was allowed to cool to room temperature and the solid product removed by filtration and washed well with water. After recrystallization thereof from acetone and drying, there was obtained 61.6 parts (60% of theory) of 2,6-bis(bromomethyl)naphthalene as white crystals melting at 162 178 C. Five recrystallizations from acetone raised the melting point to 1825-1840 C. The n-m-r spectrum of the product showed the absence of any methyl groups.

ArmIysis.-Calcd. for C H Br C, 45.9%; H, 3.2%; Er, 50.9%. Found: C, 45.8%; H, 3.2%; Br, 50.9%.

10 EXAMPLE II To a stirred slurry of 134 parts of sodium cyanide and 1300 parts of dimethylsulfoxide was added 168 parts of 2,6-bis(bromomethyl)naphthalene with external cooling of the reactor with an ice/water bath and with the addition being made at such a rate that the reaction mixture temperature remained at 25-28 C. After stirring for two hours under these conditions, following the completion of the addition, the solution was poured into excess ice/water and the resultant solid removed by filtration. The crude filter cake was boiled with about 300 parts of acetonitrile and the resultant mixture filtered. The filtrate was evaporated under reduced pressure, the resultant residue was suspended in about parts of a 1/ 1 diethyl ether/ methanol mixture, and the resultant solid was removed by filtration. After drying, there was thus obtained 49.5 parts (about 45% of theory) of crude 2,6- naphthylenediacetonitrile as a brown solid melting at 146 C. Recrystallization from ethyl acetate, followed by a separate recrystallization from a 1/1 by volume acetone/ethanol mixture, afiorded 8.7 parts (8% of theory) of pure 2,6-naphthylenediacetonitrile as white crystals melting at 162-165 C. An additional recrystallization raised the melting point of the product to 163.5- 16S.5 C.

Analysis.Calcd. for C H N C, 81.5%; H, 4.9%; N, 13.6%. Found: C, 81.4%; H, 5.1%; N, 13.2%.

An alternative preparation afforded a better yield of purer product. Thus, a mixture of parts of 2,6- bis(bromomethyl)naphthalene, 113 parts of dry sodium cyanide, and 2400 parts of methanol was stirred with heating at the reflux overnight (15 hours). Approximately two-thirds of the solvent was then removed under reduced pressure, and the resultant residue was diluted with excess water. The resulting dark solid was removed by filtration and solid extracted with 1550 parts of boiling acetonitrile. The resulting extract was filtered, the filtrate was treated with a commercially available decolorizing charcoal which was removed by filtration, and the resultant filtrate was then evaporated. Recrystallization of the resultant solid from a 1/1 by volume acetone/ethanol mixture, again adding some commercially available decolorizing charcoal, gave after filtration and drying 27.7 parts (25% of theory) of pure 2,6-naphthylenediacetonitrile as nearly white crystals metling at 163-164 C. The product can also be named 2,6-bis(cyanornethy1)naphthalene EXAMPLE III To the dry sodium ethoxide prepared from 2.02 parts of sodium and 48 parts of ethanol was added 8.7 parts of 2,6-naphthylenediacetonitrile, 13 parts of toluene, and 50 parts of diethyl carbonate. The resulting mixture was stirred with heating as solvent was distilled from. the fiask, i.e., the ethanol/toluene binary was removed by distillation. Additional toluene was added to the reactor at the same rate the distillate was collected. When the temperature of the distillate reached 115 C, the mixture was cooled and poured into an excess of ice and 10% aqueous hydrochloric acid. The resulting solid product was removed by filtration and extracted with about 200 parts of methylene chloride. The resultant methylene chloride extract was heated with a commercial decolorizing charcoal, which was then removed by filtration, and the resulting filtrate was evaporated to dryness. The solid residue resulting was suspended in about 50 parts of a 1/1 by volume diethyl ether/pentane mixture and filtered. On drying, there was thus obtained 16 parts of tan solid. Recrystallization from diethyl ether afforded 10 parts (68% of theory) of a mixture of DL- and meso- 2,6-naphthylenebis(ethylcyanoacetate) as white crystals melting at 118120.5 C.

Analysis.Calcd. for C H N O C, 68.6%; H, 5.2%; N, 8.0%. Found: C, 68.5%; H, 5.1%; N, 8.1%.

1 1 EXAMPLE IV Ten parts of 2,6-naphthylenebis(ethylcyanoacetate) was heated at steam bath temperatures with 125 parts of concentrated ammonium hydroxide for 1.5 hours. After dilution with about 125 parts of water, the resultant solid was removed by filtration, washed with water, cold acetonitrile, and diethyl ether, and fiinally dried on the filter. There was thus obtained 6.8 parts of crude 2,6-naphthylenebis(cyanoacetamide) as a white solid melting at 215238 C. with decomposition. A sample was recrystallized for analytical purposes from acetonitrile, affording the pure 2,6-naphthylenebis(cyanoacetamide) as white crystals melting at 253258 C. with decomposition.

Analysis.Calcd. for c d-1 N C, 65.7%; H, 4.1%; N, 19.2%. Found: C, 65.7%; H, 4.1%; N, 18.9%.

The purity of the main product was improved by boiling with about 150 parts of acetonitrile, cooling, and filtering. After drying, there was thus recovered 2.7 parts of pure 2,6-naphthylenebis(cyanoacetamide) as white crystals melting at 265-268 C. with decomposition. The variable melting point is attributed to the presence of a mixture of DL- and meso-isomers.

The ammonolysis can also be carried out without heat ing. Thus, a mixture of 48.5 parts of 2,6-naphthylenebis (ethylcyanoacetate) and 1200 parts of concentrated ammonium hydroxide was stirred at room temperature over night, then diluted with an equal volume of water, and the resultant solid removed by filtration. The crude, dried filter cake was twice extracted with boiling acetonitrile, leaving after drying 8.1 parts of 2,6-naphthylenebis(cyanoacetamide) as a white solid melting at 255260 C. with decomposition.

EXAMPLE V A mixture of 5.5 parts of 2,6-naphthylenebis(cyanoacetamide), 4.4 parts of sodium chloride, 390 parts of acetonitrile, two drops of pyridine, and 1.54 parts of phosphorus oxychloride was stirred at the reflux under nitrogen for 20 hours. The resulting mixture was cooled and poured into excess cold water. The resulting solid was removed by filtration, affording 4.45 parts of crude 2,6- naphthylenedimalononitrile as a tan solid melting at 222-232 C. with decomposition. Recrystallization from acetonitrile afforded 2.5 parts of pure 2,6-naphthylenedimalononitrile as white crystals metling at 238-241 C. with decomposition. A still further recrystallization raised the melting point to 24l-243 C. with decomposition. The product can also be identified as 11,11,12,12- tetracyano-Z,G-dimethylnahpthalene.

Analysie-Calcd for C H N C, 75.0%; H, 3.2% N, 21.9%. Found: C, 75.0%; H, 3.2%; N, 21.6%.

EXAMPLE VI To a warm solution of 0.5 part of 2,6-naphthylenedimalononitrile and 20 parts of acetonitrile was added 0.9 part of N-iodosuccinimide. A dark color formed at once. The solvent was removed under reduced pressure, and the residue was suspended in about 100 parts of cyclohexane and filtered. The filter cake was washed well with cyclohexane to remove the iodine and with water to remove the succinimide. There remained 0.5 part (100% of theory) of crude 11,11,12,12-tetracyanonaphtho-2,6- quinodimethan as purple microcrystals which begin to melt at 372 C. A portion of the product (0.285 part) was dissolved in approximately 940 parts of acetronitrile and filtered. The resulting solution was poured over a column of 200 parts of a commercially available chromatographic silicate and eluted with approximately 2300 parts of acetonitrile. The solvent was removed from the eluate by disillation under reduced pressure and the resultant solid residue recrystallized from acetonitrile, affording 0.11 pant of pure 1'1,11,12,IZ-tetracyanonaphtho- 2,6-quinodimethan as metallic purple plates which gave some red-brown coloration at 340 C. but did not melt 12 up to 420 C. Polarographic reduction of the product showed two equal reduction waves with =+0.21 volt and 0.l7 volt corresponding to reduction, first, to the anion radical and then to the dianion. The electrical resistivity of the product on a powder compact by the two-probe technique was 4.6 10 ohm-cm.

Analysis.-Calcd. for C H N C, 75.6%; H, 2.4% N, 22.0%. Found: C, 75.5%; H, 2.4%; N, 22.1%.

EXAMPLE VII A mixture of 0.05 part of TNAP and 0.05 part of potassium iodide in 12 parts of acetonitrile was warmed on the steam bath for ten minutes and then filtered. The resulting green solid was washed with acetonitrile, water, and again with acetonitrile. The product was then boiled with 20 parts of acetonitrile and filtered hot, affording 0.058 part of potassium tetracyanonaphthoquinodimeth anide as a bright green solid. The product is paramagnetic and exhibits an electrical resistivity on a powder compact by the two-probe technique of 53 ohm-cm. The ultraviolet spectrum of the product in acetonitrile solution indicates the absence of any neutral TNAP. Solutions of the ion radical appear red.

AntzIysis.-Calcd. for C H N K: C, 65.5%; H, 2.1%; N, 19.1%. Found: C, 65.9%; H, 2.2%; N, 19.1%.

EXAMPLE VIII To a warm mixture of 0.1 part of TNAP and 27 parts of acetonitrile was added 0.2 part of sodium iodide. After letting the reaction mixture stand for 30 minutes at room temperature, the solid was removed by filtration. After drying, there was thus obtained 0.105 part (96% of theory) of sodium 11,11,12,12tetracyanonaphtho-2,6- quinodimethanide as a dark blue solid. The ultraviolet spectrum showed the absence of any neutral TNAP. The electrical resistivity of the product was 2.7 10 ohm-cm.

Analysis.-Calcd. for C H N N-a: C, 69.3%; H, 2.2%; N, 20.2%; Na, 8.3%. Found: C, 69.5%; H, 2.7%; N, 20.9%; Na, 7.2%.

EXAMPLE IX A mixture of 0.1 part of TNAP, 0.24 part of N-npropylquinolinium iodide, and 47 parts of acetonitrile was stirred under nitrogen and heated to the reflux. The resulting red solution was filtered hot and the filtrate evaporated at reduced pressure. The residue was suspended in ethanol and filtered. The filter cake was washed with ethanol, and, after drying, there was thus obtained 0.04 part of the 2/ 3 N-n-propylquinolinium/ TNAP complex charge-transfer compound as black microcrystals melting at approximately 200 C. with decomposition. The product exhibited a volume resistivity on a powder compact by the two-probe technique of 10 ohm-cm. The product has the formulation and is thus a complex anion-radical charge-transfer salt with combined neutral species of the anion-radical-forming species.

Analysis.-Calcd. for C H N C, 78.1%; H, 4.2%; N, 17.7%. Found: C, 77.8%; H, 4.4%; N, 17.6%.

EXAMPLE X A mixture of 0.05 part of TNAP and 50 parts of acetonitrile was warmed at steam bath temperatures and 0.07 part of methyltriphenylphosphonium iodide added thereto. The reaction mixture was heated for five minutes at steam bath temperatures and the deep red reaction mixture was then filtered. The filtrate was concentrated at reduced pressure to about one-fourth the original volume. The solid black needle-s which formed were re- 13 moved by filtration, washed on the filter with ethanol, and subsequently dried. There was thus obtained 0.046 part of the methyltriphenylphosphonium /TNAP /TNAP complex anion-radical salt as fine black needles which sinter at about 200 C. but do not melt up to 400 C. The spectrum of the product obtained in acetonitrile solution showed absorption peaks at 472 m with an extinction coefficient of 100,000 and 1105 m with an extinction co- 6fiIClB1'lt of 63,000. The resistivity of the complex anionradical salt as obtained on a powder compaction by the two-probe technique was 84 ohm-cm.

Analysis.Calcd. for C I-I N P: C, 78.0%; H, 3.8%; N, 14.3%. Found: C, 78.1; H, 3.9%; N, 14.0%.

By virtue of their generically deep colors, the single crystals of the TNAP/Lewis base charge-transfer 60 111- pounds find utility as the coloring material in marking instruments such as a conventional pencil type wherein the fabricated single crystal serves as the equivalent of the lead. By virtue of the strong broad absorption in the near infra red region, particularly for the most desirable TNAP/Lewis base charge-transfer compounds which exhibit a detectable paramagnetic resonance absorption, marks made by such marking instruments are readll y and easily copied by the desirable cheap thermographi-c processes. In the larger single-crystal form, the TNAP/Lewis base charge-transfer compounds, because of their attractive shape and appearance, being colored yet highly reflective on some of the crystal planes, find use as decorative materials, e.g., as the equlvalent of gem stones in jewelry, and the like. Similarly, in the smaller single-crystal form, the TNAP/Lewis base chargetransfer compounds find artistic and decorative ut1l1ty, for instance, as pearlescent materials in otherwise colorless plastics, or pearlescent pigment materials for decorative lacquers and plastic solutions.

These charge-transfer complexes of TNAP with P1 or Lewis bases are generically colored, usually with characteristic deep shades of color. Accordingly, the formation of these complexes with TNAP is basis fora method involving the detection and identification of Lewis bases. These charge-transfer complexes have other uses, both per se and again in the formation thereof. Thus, the TNAP/Lewis base complexes with the stronger Lewis bases are para-magnetic and thus have usefulness in recognized uses for paramagnetic materials. These paramagnetic complexes are generically characterized by exhibiting paramagnetic absorption in the electron paramagnetic resonance spectrum (EPR absorption). A still further use of the TNAP/Lewis base chargetransfer complexes, which are paramagnetic, resides in an additional characteristic physical property of such complexes. Thus, the TNAP charge transfer complexes with the stronger Pi or Lewis bases exhibit strong, broad absorption in the near infrared region, e.g., from 0.5 to 2.0 microns, generally centered around 1.0 micron. Based on this property, such charge-transfer complexes find significant use as the coloring agent, or pigment, in writing inks which make possible reproduction of text matter by thermographic processes.

Ther-mographic copying represents a convenient and easy method of rapidly copying text material dry. However, operability of the process requires that the text material to be copied must absorb in the infrared. Otherwise there is no heat buildup and accordingly no copy is formed on the thermographic paper. Printed material, wherein the text matter is in pigmented inks, is satisfactory since the pigment materials for these inks do absorb in the infrared. The same is true of typewritten matter, whether it be the original copy or carbon copies thereof, since again the text matter is defined by carbon particles which absorb in the infrared. However, most fountain pen inks, and in particular ballpoint inks, achieve their characteristic color through the use of dyes, and in some few instances pigments, which do not absorb in the infrared but only in the visible. Accordingly, text matter appearing in these types of inks cannot be copied by a thermographic process. The paramagnetic TNAP/Lewis base charge-transfer complexes in absorbing in the near infrared permit direct, ready, and easy thermographic copying of lettertext matter defined by inks carrying these complexes as the coloring, or pigmenting, agent.

These T NAP charge-transfer complexes are generically colored and accordingly find use in any of the many wellknown and established uses for colored materials. Thus, in the case of the colored solutions, these are useful in obtaining decorative color effects. In the case of the TNAP charge-transfer complexes with stronger Lewis bases, the complexes are colored solids irrespective of whether the complex is paramagnetic or not. These colored solid complexes find use in any of the many wellestablished fields, such as dyes and pigments, for both paints and plastics, and colored fillers for the latter.

Since all the TNAP charge-transfer complexes are colored, the controlled formation thereof forms the basis for still another use, viz., the reproduction of text matter by impact printing, i.e., by the pressure formation of graphic images. Thus, one sheet of a carrier, e.g., paper, is impregnated with a solution of TNAP and the solvent removed via evaporation, leaving the TNAP deposited in, on, and through the paper carrier. Another separate sheet of paper is similarly so treated with a Lewis base. A laminate of the two sheets will reproduce a colored image in the second sheet made by pressure on the first sheet.

The present invention is also generic to the chargetransfer compounds of TNAP with organic and organoinorganic Lewis bases in crystalline form, including both microcrystal and single crystal form. This latter term is used in its art-recognized sense as meaning an integral body of solid matter containing an ordered periodic arrangement of atoms which extends unchanged throughout the body without discontinuity or change of orientation. As is apparent from the foregoing, these TNAP/organic or organ c-inorganic Lewis base charge-transfer compounds can readily be prepared by contacting TNAP with the approprate Lewis base, generally in an inert reaction medium. If the reaction is carried out quickly and at modest temperatures, the charge-transfer compounds are obtained in a polycrystalline state, i.e., as a mass of micro-crystals. If, however, the crystals are permitted to form slowly from the inert medium, for instance, by mixing solution of TNA'P and the appropriate Lewis base, preferably at elevated temperatures, and slowly permitting the reaction medium to cool, single crystals of the TNAP/ Lewis base charge-transfer compounds can readily be obtained,

As stated in the foregoing, the present invention is generic to the charge-transfer compounds of TNAP with Lewis bases. These charge-transfer compounds vary in structure and properties, primarily as a function of the relative base strengths of the Lewis bases involved, and accordingly include those compounds which are probably more properly referred to as complexes wherein in the equilibrium stable state there is no detectable charge transfer between the Lewis acid component, i.e., the TNAP, and the Lewis base component. These materials are believed to be properly describable as Pi complexes involving semibonding atomic orbital overlap between the Pi orbitals of the Lewis acid and Lewis base components.

The more important charge-transfer compounds of TNAP are the charge-transfer compounds wherein in the ground equilibrium state there exists a formalized charge transfer between the Lewis acid and Lewis base components. In these compounds, an electron has been donated by the Lewis base component and accepted by the Lewis acid component, i.e., the TNAP, and accordingly in the equilibrium representation of the ground state of such compounds, the TNAP component exists in the form of the corresponding anion radical or TNAPide, i.e.,

TNAP

Depending on the base strength of the Lewis acid com ponents in these charge-transfer compounds, there are two normal types of such compounds. The first of these are those with the moderately strong Lewis bases, which are best describable as the simple anion-radical salts, wherein, on a stoichiometric basis to attain equilibrium electronic neutrality in the said charge-transfer compounds, the over-all molecular structure of the said compounds will consist of the cation involved (or cations in the case of mixed salts) and the TNAPide in amount such as to give electronic neutrality in the over-all salt.

The second of these are the complex anion-radical salts wherein, in addition to the requisite numbers of the TNAP anion radicals to assure electronic neutrality to the over-all charge-transfer compound, there are also present one or more molar proportions of bound or combined TNAP which, while bound into the molecular structure of the said complex anion-radical salt, are still electronically neutral. While it is not known with any certainty, it is believed that the anion-radical TNAPide moieties are bound into the over-all molecular structure of the complex anion-radical salts by formal electronic equilibrium bondings to the cation, and that the bound or combined neutral molecules of TNAP are bound into the over-all molecular structure of the complex anion-radical salts through Pi orbital overlaps of the said neutral moieties with the said anion-radical moieties.

Probably the most interesting physical properties of these new materials are to be found in the electrical behavior thereof; the complex anion-radical salts exhibit low electrical resistivity, or conversely high electrical conductivity. The electrical resistivity of the most outstanding of these salts permits classification of these materials as conductors and also high-resistivity-metal-like compounds.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. 11,1 1, l2, l2-tetracyanonaphtho-2,G-quinodimethan.

2. A Pi complex of 11,11,12,l2-tetracyanonaphtho-2,6 quinodimethan with a Lewis base.

3. A salt charge-transfer compound of the 11,11,12,l2- tetracyanonaphtho-Z,6-quinodimethan anion radical with the cation of a Lewis base.

4. A salt charge-transfer compound of the formula wherein M is the cation of a Lewis base; It is the formal positive charge on the cation M; x is the number of said cation species present, which in the plural instance includes mixed individual cations; TNAP is the 11,1l,12,l2- tetracyanonaphtho-2,6-quinodimethan moiety; indicates a negative ionic charge and an. electron; y is the number of negatively charged TNAP species present; and

nx is the total negative charge on the charged TNAP moieties. 5. A salt charge-transfer compound of the formula wherein M is the cation of a Lewis base; It is the formal positive charge on the cation M; x is the number of said cation species present, which in the plural instance includes mixed individual cations; TNAP is the 11,ll,l2,l2 tetracyanonaphtho-2,6-quinodimethan moiety; indicates a negative ionic charge and an electron; is the number of negatively charged TNAP species present; nx is the total negative charge on the charged TNAP moieties; indicates the combined neutral TNAP species; and z is the number of combined neutral TNAP species present.

6. Potassium l1,11,12,lZ-tetracyanonaptho-Z,6-quinodimethanide.

7. Sodium 1l,l1,12,l2-tetracyanonaphtho-2-6-quinodimethanide.

8. The salt charge-transfer compound of the formula [N-n-propylquinolinium [TNAP [TNAP] wherein TNAP is the 11,1l,l2,l2-tetracyanonaphtho-2,6- quinodimethan moiety; indicates a negative ionic charge and an electron; and indicates the combined neutral TNAP species.

9. The salt charge-transfer compound of the formula [methyltriphenylphosphonium [TNAP [TN AP] wherein TNAP is the 11,11,12,12-tetracyanonaphtho-2,6- quinodimethan moiety; indicates a negative ionic charge and an electron; and indicates the combined neutral TNAP species.

10. A process for the preparation of 1l,11,12,l2-tetracyanonaphtho-Z,6-quinodimethan, which comprises:

(1) dihalogenating 2,6-dimethylnaphthalene, thereby forming a 2,6-bis(halomethyl)naphthalene;

(2) reacting said 2,6-bis(halomethyl)naphthalene with a cyanide salt, thereby forming 2,6-naphthylenediacetonitrile;

(3) carboalkoxylating said 2,6-naphthylenediacetonitrile, thereby forming a 2,6-naphthylenebis(alkylcyanoacetate) (4) reacting said 2,6-naphthylenebis(alkylcyanoacetate) with an ammonia source, thereby forming 2,6- naphthylenebis cyanoacetamide) (5) dehydrating said 2,6 naphthylenebis(cyanoacetamide), thereby forming 2,6-naphthylenedimalononitrile; and

(6) dehydrogenating said 2,G-naphthylenedimalononitrile, thereby forming the aforesaid 11,1 1,12,12-tetracyanonaphtho-2,6-quinodimethan.

References Cited by the Examiner UNITED STATES PATENTS 7 3,115,506 12/1963 Acker et al 260396 WALTER A. MODANCE, Primary Examiner.

IRVING MARCUS, NICHOLAS S. RIZZO, Examiner. 

1. 11, 11, 12, 12-TETRACYANONAPHTHO-2,6-QUINODIMETHAN.
 8. THE SALT CHARGE-TRANSFER COMPOUND OF THE FORMULA 